1. Field of the Invention
The present invention relates to a power supplying apparatus for supplying power to a plurality of loads such as a plurality of cell modules, a plurality of cell controlling modules, and a plurality of voltage measuring apparatuses, etc.
2. Description of the Related Art
In recent years, in order to achieve environmental conservation, low noise, and low fuel consumption, electric vehicles such as an electric car, a fuel-cell car, and a hybrid car are in practical use, and these electric vehicles are equipped with high-voltage batteries for driving traction motors. Generally, the high-voltage battery used for the above purpose is achieved by connecting a plurality of cell modules in series. Because a current passing through the traction motor is lowered by heightening voltage of the battery as described above, a mass of an electric wire and a heat loss caused by power consumption can be lowered compared to a low-voltage and same-output traction motor.
Incidentally, in a plurality of cell modules connected in series (battery cell), a charged amount of one battery cell will become different from that of other battery cell by degrees due to a deviation of a characteristic of the battery cell (for example, a deviation of an internal impedance of the battery cell) after charging/discharging are repeated. Therefore, when any one of battery cells arrives at an upper limit of the charged amount, a charging operation should be stopped even if other battery cells are not full charged. Also, when any one of the battery cells arrives at a lower limit of the charged amount (discharge cut off voltage), discharging operation should be stopped even if other cells do not arrive at the discharge cut off voltage. That is, as a whole group of cells connected in series (assembled battery), because any one of the battery cells arrives at the upper or lower limit of the charged amount at early stage, available charged amount is substantially reduced.
For this reason, in order to resolve the above problem, a charging apparatus in which each electrode of a capacitor cell (battery cell) is isolated from a cycle power source via a capacitor, this capacitor is charged by voltage corresponding to a potential difference between a potential of each electrode and an output voltage of the cycle power source, thereby charging the battery cell (for example, see JP 2008-092717 A). This charging apparatus includes a condenser (high-voltage battery) in which a plurality of capacitor cells are connected in series, and an electrode of any one of capacitor cells is defined as a reference potential point; a plurality of capacitors connected in series in which a voltage of one end is fixed via a rectifier between one electrode of each capacitor cell and another electrode of the plurality of capacitor cells; and a cycle power source which is connected to a reference potential point of a condenser which is connected between any other end of the plurality of capacitor connected in series and a reference potential point of the condenser, and generates a repeated signal. With such configuration, because a charging current is allowed to pass from a battery cell having high charging voltage to a battery cell having low charging voltage, deviation of voltage of battery cell is decreased, resulting in an increased available charged amount of whole group of cells.
Also, voltage measuring apparatuses, which alternately measures a voltage of each cell module which constitutes the group of cells using a switch element composed of a Pch MOS-FET and a Nch MOS-FET, is disclosed (for example, see JP 4095089 B2). According to this apparatus, because a high-speed switch element composed of the Pch MOS-FET and the Nch MOS-FET is used, the voltage of each cell module can be measured with high-accuracy and high-speed when the group of cells is in process of charging/discharging. As a result, the deviation of the voltage of each cell modules can be detected at early stage so as to take an appropriate action.
Further, an apparatus, which measures a voltage of each cell module which constitutes an assembled battery by a monitoring unit, electrically isolates the voltage measured by the monitoring unit via a photo coupler, and transmits the isolated voltage to an outer controlling unit, is disclosed (for example, see JP 08-140204 A). According to this apparatus, because a voltage path of the assembled battery is isolated from a voltage path of the controlling unit via the photo coupler, for example, even if the voltage of the assembled battery is high, high voltage is not applied to the controlling unit. For this reason, there is no fear of voltage breakdown of the controlling unit caused by high voltage of the assembled battery. Also, because a withstand voltage of the controlling unit can be lowered, low cost of the controlling unit can be achieved.
However, the charging apparatus disclosed in JP 2008-092717 A needs a cycle power source to generate AC voltage which is the repeated signal. Also, a specific storage battery cell (or a specific cell module composed of a plurality of storage battery cells connected in series) can be charged, but can not be discharged. That is, in order to allow the specific cell module to be discharged, it is necessary to combine the cell module with a discharge circuit composed of a resistor, etc. This combination allows the charged amount of the cell modules to be wasted as Joule's heat, and this is an undesirable result from the viewpoint of an effective use of energy of cell. Also, in apparatuses disclosed in JP 4095089 B2 and JP 08-140204 A, in order to operate a measuring circuit to measure a voltage of the cell module, it is necessary to use a DC/DC converting power supply (DC/DC converter) whose breakdown voltage (for example, 400 V) is higher than the voltage of the assembled battery, or to use the target cell (i.e., the cell module) as the power supply. Therefore, a configuration of the measuring circuit to measure the voltage of the cell module becomes complicated.
Further, in apparatuses disclosed in JP 4095089 B2 and JP 08-140204 A, a configuration in which cell controlling module circuit are sequentially connected to an assembled battery is disclosed. However, when a DC/DC converter is used for every cell controlling module circuit as a power supply to operate this cell controlling module circuit, a power supply apparatus becomes expensive because the more the number of cells in the assembled battery, the higher the breakdown voltage of the DC/DC converter. Also, when the target assembled battery is used as a power supply, the assembled battery may be discharged by the cell controlling module circuit during non-operating time period. For this reason, if the cell controlling module circuit is isolated from the power supply in order to decrease a discharged amount of the assembled battery, some kind of power to activate the cell controlling module circuit is needed. Also, when the target is a fuel cell, the fuel cell may not be used as the power supply because a voltage on the fuel cell side may be lower than a minimum operating voltage of the cell controlling module circuit.
A power supplying apparatus, which supplies power to a plurality of loads such as a plurality of measuring circuits and a plurality of cell controlling module circuits, etc to measure charged amounts of a plurality of cell modules and voltages of a plurality of cell modules, has been needed.
Therefore, an object of the present invention is to provide a power supplying apparatus for supplying power to a plurality of loads.